1. Field of the Invention
The present invention relates to a process for preparing difructose dianhydride III, hereinafter referred to as "DFA III".
2. Description of the Prior Art
DFA III is a disaccharide having the structure in which two molecules of fructose are condensed with dehydration via 1-2' and 2-3' linkages, and has been isolated and identified in 1931 by Jackson et al.: Bur. stand. J. Res., 6, 709 (1931).
DFA III may notably be regarded as a low-calorie sweetener since it is not metabolized nor fermented in animal bodies and is expected to be utilized in various applications, including use for a diet food, in the future.
Jackson et al. (supra) prepared DFA III by acid hydrolysis from inulin, which is a polysaccharide mainly composed of fructose. However, the yield was merely no more than about 2%. Thus, the process employed by them is not efficient.
In 1972, Tanaka et al. prepared DFA III from inulin by means of an inulin lytic enzyme produced by Arthrobacter ureafaciens: Biochim. Biophys. Acta, 284, 248 (1972). However, this enzyme is highly sensitive to temperature; it will be rapidly inactivated above 60.degree. C. Thus, this enzyme cannot be suitable for industrial production of DFA III.